The present invention relates to an exhaust-gas cooler.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
Exhaust-gas coolers of a type involved here find application in an EGR system which recirculates exhaust gas from an internal combustion engine to cool the exhaust gas for recirculation. The cooled exhaust-gas recirculation suppresses generation of nitrogen oxides by dropping the combustion temperature in the cylinders of diesel engines for example. An exhaust-gas recirculation valve is used to control an amount of exhaust gas to be conducted through the exhaust-gas cooler after combustion. The exhaust gas is then fed to fresh air required for the combustion process. As a result of the addition of exhaust gas to fresh air, oxygen concentration in the cylinders is lowered and thus the combustion temperature. Cooling the exhaust gas reinforces this effect.
FIG. 1 is an example of a conventional exhaust-gas cooler 1 having a so-called I-configuration. The exhaust-gas cooler 1 has a housing 2 with an inlet side 3 on one end face and an outlet side 4 on the opposite end face. Exhaust gas enters the inlet side 3 via an exhaust-gas entry zone 5 into the housing 2. Arranged in the exhaust-gas entry zone 5 is a control element 6 which pivots about an axis 11 and is constructed to conduct the incoming exhaust-gas flow either to a bypass duct 7 or to a cooling zone 8. The cooling zone 8 has an exhaust-gas cooling duct 9 which extends axially from the entry zone 5 in the direction of an exhaust-gas exit zone 10 on the outlet side 4. In the event, no cooling is desired, for example during initial start or cold start of the internal combustion engine, the control element 6 is switched to allow the flow of exhaust gas to bypass the cooling zone and to flow through the bypass duct which extends over its entire length dimension in parallel relationship to the cooling zone and the exhaust-gas cooling duct 9.
FIG. 2 is another example of a conventional exhaust-gas cooler 12 having a so-called U-configuration with a cartridge-like housing 13. The exhaust-gas cooler 12 has an exhaust-gas cooling duct 9 which extends in the shape of a U through the cooling zone 8. This is shown in FIG. 3. The bypass duct 7 is arranged on the front end and extends perpendicular to the cooling zone 8 or exhaust-gas cooling duct 9. The control element 6 is hereby arranged in the bypass duct 7.
It would be desirable and advantageous to provide an improved exhaust-gas cooler to obviate prior art shortcomings and to significantly improve the cooling capacity in a simple and yet reliable manner.